What's the difference between Instant Reporting and a traditional report?

Depending on the size of data requested, traditional reports typically take about 5 minutes to download, whereas once an Instant Report is requested, you’ll receive an email with your report in less than a minute.
Traditional reports are offline, whereas Instant Reporting downloads in less than 3 seconds.
Traditional reports are offline, whereas Instant Reporting allows you to drag and drop data to build a report in real time.
A traditional report has a limited number of metrics and dimensions, whereas Instant Reporting gives you the ability to create your own metrics and dimensions.

What’s the difference between Instant Reporting and a traditional report?